The instant invention relates generally to ship ballasting systems and more particularly to a ballasting system using membranes that separate the oil and the water ballast therefore eliminates oil contamination and water pollution.
It is well known in the art of ships and particularly oil tankers that the ship rides dangerously high in the water when its fuel tanks, oil cargo tanks, or cargo holds are empty. The ship lacks roll stability, is subject to severe bending stresses in hog and sag, steerage is difficult, and the ride gives discomfort to the crew. For these reasons, it is common practice to "ballast" the ship by filling the tanks and holds with seawater when they are empty or even when partially empty of oil. Further, it is the practice to pump in ballasting water to facilitate the pumping out of the oil cargo from oil tankers.
Heretofore, there have been no attempts made to positively separate the oil and the water ballast because they are considered substantially immiscible and have different specific gravities with oil being the lighter and therefore always floating on top of the water. However, it is possible for the oil and water to emulsify particularly at the interface due to churning during pumping or sloshing during transit. For this reason, when off-loading a cargo of oil, some water is carried over to contaminate the delivered oil. Also, moisture-laden air vented into the tank causes water build-up. Furthermore, a particular problem exists when the tanker takes on a load of oil and deballasts at the same time in that a significant amount of oil goes overboard entrained with the ballast water to contaminate and pollute the area. This oil eventually finds its way to local beaches making them unfit for use and kills much wildlife.
Another problem associated with the state-of-the-art ballasting method is that it contributes greatly to repair costs of the ship because the seawater causes corrosion in the tanks. Periodically, the tanks must be drained, steam cleaned, scaled, and repainted. If the tanker has been carrying gasoline or other highly flammable products, this repair is extremely dangerous. It is also obvious that this old ballasting method is wasteful of the contaminated portion of oil, be it crude oil, heating oil, jet fuel, or gasoline cargo or fuel for the ship's propulsion.